A non-invasive, real-time, in vivo imaging procedure has been developed for directly determining the spatial distributions of blood flow, by measuring the infrared (IR) emission from the skin of an individual. The procedure does not require direct contact between the instrument and the patient. The imaging system utilizes an IR imaging camera, and a computer to store the stream of two-dimensional images and analyze data for calculating the distribution of low frequency oscillations of temperature. Patients were adapted to room temperature over 20 min and, after that, remained immobile for one min (to obtain the blood flow distribution image) and/or 5-20 min minutes during data acquisition for assessment of low frequency vasomotion. Data analyses were performed later using computer software developed in the laboratory. Measurements were made from the palmar surface of the hand or forearm. IR demonstrated dose-response patterns of spatial and temporal distribution of blood flow during acetylcholine, sodium nitroprusside and L-arginine infusions in real time. Preliminary data showed that IR- and plethysmography-derived hyperemia indexes were significantly correlated. These noninvasive tests require no special illumination, and can be used to assess microvascular recruitment and vascular tone in the periphery vascular bed.